<!DOCTYPE html>
<html lang="zc-CN">

<head>
    <meta charset="UTF-8">
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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>

    <script>
        let num1 = +prompt('请输入第一个数')
        let num2 = +prompt('请输入第二个数')
        let sum1 = 0
        function sum(a, b) {
            sum1 = a + b
            return sum1
        }
        let res = sum(num1, num2)
        console.log(res);
    </script>
</body>

</html>